Air lock coal scale



Dec. 1, 1953 A. J. sTocK AIR LOCK COAL SCALE 6 Sheets-Sheet l Filed Oct.51, 1951 INVENTOR Dec. 1, 1953 Filed Oct. 31, 1951 A. J. sTocK AIR LocxCOAL SCALE,

6 sheets-sheet 2 4 INVENTOR ATTORNEYS Dec. 1, 1953 Filed Oct. 51 J 1951A. J. s'rocK 2,661,181

AIR LOCK COAL SCALE 6 Sheets-Sheet 3 4,18 on ,m 1,20

INVENTOR ATTORNEYS Dec. l, 1953 A. J. sTocK 2,661,181

AIR LOCK COAL SCALE Filed Oct. 3l, 195] 6 Sheets-Sheet 4 INVENTORATTORNEYS 4M/wlw@ BY @M Dec. l, 1953 A. J. s'rocK 2,651,181

AIR LOCK COAL SCALE Filed 0G12. 3l, 1951 5 Sheets-Sheet 5 1J J W umATTORN E YS BY www QW l www Dec. 1, 1953 A. J. sTocK 2,661,181

AIR Loox COAL SCALE Filed 0G12. 51, 1951 S Sheets-Sheet 6 u 2D @f3/3OOOQG@ OOGOOOO.

INVENTOR ATTORNEYS atented Dec. l, 1953 UNITED STATES PATENT OFFICE AIRLOCK lCOAL SCALE Arthur J. Stock, Cleveland, Ohio Application October31, 1951, Serial No. 254,130

9 Claims.

This invention relates to a bulk material scale apparatus for operationwith a system under pressure and more particularly vto a coal scale foruse with either pressure or vacuum furnaces or burners.

In the handling of bulk material wherein it is transported from astarting point at atmospheric pressure through a weighing operation to aremote point under pressure, a stoppage of the bulk material willgenerally result in gases or vapors being blown back through the systemfrom the remote point under pressure. These gases generally contain dustor other obnoxious impurities and usually gain access to the atmosphereat the starting point thereby polluting the surrounding area andresulting in the discomfiture of persons in the immediate vicinity.Similar difficulties are encountered when the lremote point is undervacuum where it is desirable to prevent the entry of air at the startingpoint.

While this problem is present in all types of bulk material systems ofthis nature, nevertheless, it has particular reference to coal handlinginstallations feeding pressure or vacuum furnaces or burners where thereis an added danger of fire. A normal coal installation of this typestores the coal in a bunker for transportation through a feeding systemincluding conveyors, a scale apparatus, chutes, downspouts and a feeder,to a pressure or vacuum furnace.

In order to burn coal in very large boiler furnaces, it has been thecustom in many installations to first pulverize the coal and then blowthe powdered coal into the furnace where it burns as a gas. Equipmentnecessary to carry out the foregoing operation consists of a pulverzer,a feeder for that pulverizer, and a fan which picks up air andpulverized coal and forces that combustible mixture into the boilerfurnace.

One arrangement of equipment places the fan between the pulverizer andthe boiler furnace. If the pressure within the boiler furnace isslightly negative, as it usually is, then the interior of the pulverizeris under a small vacuum. Consequently, if the coal feed pipe between thecoal feeder and the pulverizer were left open to the atmosphere, most ofthe combustion air would rush through this pipe. Therefore the feed pipeis made airtight by constantly having a solid head of crushed coal ofseveral feet located therein to act as a reasonably good air sealbetween the atmosphere and the interior of the pulverizer, and thus onlya small quantity of cold air leaks into the pulverizer.

With the arrangement as suggested above there is some wear on the bladesof the fan due to the erosion caused by the coal dust from thepulverizer moving over the fan blades. In order to reduce fanmaintenance, some installations place the fan ahead of the pulverizer.This puts the pulverizer under positive pressure and also the pulveriaerfeeder. Here again, a column of coal several feet high ahead of thepulverizer feeder has been used as a seal to prevent loss of air intothe atmosphere through the coal.

It is desired in many installations to preheat the combustion air. Henceit is necessary to reduce to a minimum the leakage through the feedpipe.

The above and foregoing remarks have been made in reference to a boilerfurnace operating under a slight negative pressure by reason of theutilization therewith of an induced draft fan. However, the more recenttendency is to utilize a forced draft fan. This means that the boilerfurnace operates under a positive pressure, and as a result the'pressureexisting at the pulverizer feeder is several times as great as it waswith installations employing an induced draft fan. Therefore, in orderto prevent leakage of air back through the coal as it is fed to thepulverizer feeder, it is necessary to provide a higher column of coal inthe feed pipe to form a satisfactory seal.

Also during the recent years there has been developed another method offiring coal under very large boilers which is known as the cycloneburner. This burner consists of a large watercooled cylinder into whichthe coal is brought along with air under a fairly high pressure. Becauseof the high pressure on the forced draft air, there is a very high airvelocity developed as the air enters the cyclone burner. Theseconditions cause combustion to take place almost instantly with a veryminimum of excess air, and therefore the eiiiciency of this method ofcombustion is excellent. However, the high pressure of the systemnecessitates the use of a still higher head of coal in the feed pipe toform a satisfactory seal.

If a standing column of coal is used as a seal, there also is a problemwith the coal scales which are very often employed to weigh the coal asit A need be employed in order to make the coal scales accurate.

It has been found in many plants that it is impossible to provide asuicicnt column of coal ahead of the feeders in order to givesatisfactory sealing on a space or headroom basis. It has also beenfound that feeding the coal against the pressure of the air is not asreliable as it should be because wet, line, sticky coal tends to make amore perfect seal but the air pressure has a tendency to cause such coalto stop flowing entirely. Therefore, in order to insure more reliablecoal flow and also in order to reduce the overall height of the boilerplant some other method of sealing against the air pressure isnecessary.

One other such method is to use a. star-type seal or feeder between thecoal feeder and the cyclone burner. Such seals result in the coal beingfed in a succession of small batches. Therefore combustion is not assatisfactory as it would be if the feed were more uniform. Furthermorethe loss of air back through such a seal is greater than it should beand the maintenance of this type of equipment is quite high because ofthe rubbing of the star-shaped core against the housing.

Another type of seal that has been employed is the screw feeder which isrun full of coal at all times and which has a short pitch at itsdischarge end. It has been found dimcult to force the coal into thescrew at the feed end partly due to the air pressure differential thatexists across the screw and partly due to the relatively small size ofthe screw in relation to the other equipment.

In the operation of boiler plants with pressure furnaces, there alsoexists a danger, that the coal may hang up in the bunker and not flowout through the outlet provided therefor. Under these conditions, if theoperator stops the flow of feed air to the burner, the hot furnace gaseswill vent back through the system to the bunker. Inasmuch as thetemperature within the furnace is several thousand degrees, it isobvious that damage will result to the various pieces of equipmentbetween the bunker and the furnace, and also the coal that does remainin the bunker will catch on fire. This can happen almost instantly. Sucha condition is very dangerous to operators and also it may result in thecomplete stoppage of steam generation and in the case of a publicutility may shut down the entire plant. For safety of operation ofpressure furnaces, it is necessary that the system at some point aheadof the furnace be completely shut off at all times.

Accordingly, this invention provides apparatus in the nature of a bulkmaterial scale for alleviating the undesirable features in pressure ofvacuurn systems as above described. More particularly, this inventionprovides a coal scale apparatus for eliminating the danger of fires andovercoming other disadvantages of coal feeding systems operated withpressure furnaces or burners. This is accomplished by this inventionwith reference to coal handling by providing a coal scale apparatuswherein a pair of gas valves are arranged to effect a gas lock toprevent gases under pressure from traveling back through or into thesystem. At all times, at least one of the gas valves is maintainedclosed to stop any gases under pressure from moving beyond theapparatus. Further, a vent to any desired location can be provided inthe apparatus to reduce the pressure of the gases trapped in the lock tosubstantially atmospheric pressure. In order to permit the gas valves tooperate quickly and efficiently nature indicated which will preventgases under pressure from escaping at undesired points, or, in the eventof a vacuum system, lwill prevent air entering the system at the pointfrom which the bulk material is fed.

It is a further object of this invention to provide a coal scaleapparatus for use in installation systems as previously described thatwill eliminate the danger of fires and that will overcome otherdisadvantages of present systems.

It is a still further object of this invention to provide a coal scaleapparatus that will operate more efficiently and economically than anysuch apparatus presently available,

Other and further objects of the present invention will become readilyapparent from a detailed consideration of the following description whentaken in conjunction with the drawings in which:

Figure 1 is a View in side elevation partly broken away showing the coalscale apparatus of the present invention;

Figure 2 is a view in vertical section of Figure l taken along line 2 2;

Figure 3 is a view in vertical section of Figure l taken along line 3 3;

Figure 4 is a view in vertical section of Figure 2 taken along line 4 4;

Figure 5 is a view in horizontal section of Figure 4 taken along line 55;

Figure 6 is a view in vertical section of Figure 5 taken along line 6 6;

Figure is a View in vertical section of Figure 5 taken along line landFigure S is a view in side elevation partly broken away showing amodified form for operation of the gas valves.

Referring now to the drawings, Figures 1-7 inclusive illustrate the newand improved coal scale apparatus. A. main housing lil encloses anendless conveyor belt i2 carried on pulleys lll which are mounted onshafts i5 which are bearing supported in side plates 2S. A weigh hopperI8 is suspended from one end of a weigh lever mechanism to be describedhereinafter. Auxiliary housings 2l and 22 are arranged on the mainhousing is to encase and protect portions of apparatus located outsidethe main housing l. Further, an electrical compartment 25a is mounted onthe main housing iii for location of the necessary electrical equipmentfor operation of the apparatus. Each of the housings and thecornpartinent are provided with doors to permit access thereto.

Within the main housing it, the endless conveyor belt l2 is mounted onpulleys i4 as above described. Side plates 26 are mounted between shaftsl5 to securely maintain the relative positions of the pulleys l. Smallrollers 2c support the conveyor frame and allow the entire feederassembly to be removed for aelt replacement. The upper part of theconveyor belt is supported by a fiat plate Directly above the belt l2 atthis point is an opening 32 in the main housing l. Skirt plates 3 arevertically mounted on either side of belt l2 between the opening 32 andthe conveyor. Also an end plate 33 is transversely positioned across thebelt |2 at one end thereof.

The appara-tus is normally joined to a source `of coal such as a bunkerby connecting opening 52 to the bunker outlet directly or throughintermediate apparatus such as a coal valve, chute or dcwnspout or anycombination thereof. Hence, coal is fed to the belt I2 through opening32 and is transported to the right of the conveyor, as shown in Figurefl, to be dumped. A scraping bar 35 is mounted with the conveyor justbeyond the dumping point to keep coal from sticking on the belt I2during its return run. However, practical experience indicates that somecoal, particularly ne, evades the operation of scraping bar 35 andconsequently a compartment 35 is provided for the collection of thiscoal.

The coal being dumped from the conveyor belt l2 passes through anopening 38 in a plate 40 and is received in the weigh hopper I8. Twopins project from opposite sides of weigh hopper I8. The pins 42 aregiven rigidity by a conventional strut arrangement 44. A loop 46attached to one end of a shaft 48 is secured to each pin 42. The otherends of the shafts 48 project through partitions 58 which constitute onewall of each of compartments 52 and are each joined to a scale bearingloop The shafts 48 at their points of projection through partitions 5E!are encased in molded rubber bellows 5| so that the compartments 52 aremaintained pressure tight with respect to the space occupied by theweigh hopper i3. The compartments 52 communicate with the auxiliaryhousing 2 I. The scale bearing loops 54 cooperate with pivot pins 5Grigidly fastened to weigh levers 58 to provide a knife-edge attachmentfor the weigh hopper I8 with one end of the weigh levers 58. Each of theweigh levers 58 in compartments 52 is provided with a knife-edge pivotor fulcrum (not shown) by means of scalebearing loops and pins. Theother ends of the weigh levers 58 are interconnected by a bar 68 so theywill operate as a single unit. Scale-bearing loops 52 cooperate withpins 54 rigidly fastened to weigh levers 58 to form a knife-edgeattachment for a counterweight 66 with the other ends of weigh levers58. The counterweight 56 is suspended between the scale-bearing loops62.

The weigh hopper I8 is provided with a closure member 68 pivoted asindicated at 'I0 and has mounted .therewith a counterweight assembly 'I2which tends to keep closure member 68 shut. A solenoid housed incompartment I4 mounted on the weigh hopper I8 operates responsive to anelectrical circuit to hold the closure member 68 against opening duringthe weighing cycle. After the desired weight is in hopper I8, theelectrical circuit controlling the solenoid opens, thus allowing theclosure member 68 to swing open and discharge the coal from the hopperI3. Coal being dumped from the hopper |8 passes out of the apparatusthrough outlet 'I5 to a downspout, chute, or pulverizer feeder or thelike.

An electric motor 'I6 supplied from a suitable source is mounted on topof auxiliary housing 28. The motor output shaft F3 passes into auxiliaryhousing 2| where it is connected to a gear reducer 8). The output shaft82 of the gear reducer 88 passes into main housing I8 and has a gear 84mounted on its end. A gear 8&5 mounted on shaft I6 of the forward pulleyI4 of the conveyor meshes with gear 84. Accordingly, the motor 'I6 ismechanically connected to the forward pulley I4 of the conveyor andthereby power is supplied to drive the conveyor belt I2.

The space occupied by the weigh hopper I8 is completely enclosed by theplate 48 xed to Ithe main housing l@ above hopper I8 as indicated at 88,a plate 82 fixed to the main housing Il below hopper I8 as indicated atSii, a series of partitions extending between the plates lll) and 92generally indicated as 36 and part of the main housing lil. As notedpreviously, plate It is provided with an opening 38. Joined by bolts 88to plate Il@ bounding opening 38 are steel bars Idil each provided witha Stellite edge |Il2 mounted thereon. Similarly plate 82 has an openingIlfl. Jointed by bolts to plate 52 bounding opening Idil are steel barsID3 each provided with a Stellite edge II mounted thereon. Series ofrollers |I2 and I I3 each biased by a spring I ill or I I5 respectivelyare mounted on opposite sides of each of the openings 38 and |88respectively. Each of the rollers I I2 and I |3 is mounted on a diagonalelement I I8 and I II respectively, pivotally supported on an elongatedmember I i8 and lill respectively so that they are individually urgedtoward their respective opening by the spring bias. 'lliis preoisestructure will be considered in greater detail with specific referenceto Figures 5-'7 inclusive. Plates |28 and |2| preferably of stainlesssteel are carried on each series of rollers |52 and IIB respectively.

A motor |28 mounted in auxiliary housing 2li is supplied from a suitablesource of energy. The output shaft |28 of motor 28 drives a gear reduoer|38 preferably of the worm gear type. The output or low speed shaft Il-Zof reducer |38 has mounted thereon a crank |34. A link itt` has one endpivotally attached to the crank i3d and the other end pivotally attachedto crank |3'I, the other end of which is rigidly fixed to a shaft |38which projects into main housing It. This shaft |38 is mounted inbearings |48 and within main housing I8 has mounted thereon a pair oflevers |42. The other ends of levers |62 are pivotally connected to oneend of operating shafts Ille. The other ends of operating shafts lliilare pivotally joined to one side of plate IM. Hence operation of motorIES will cause levers |42 to oscillate and thereby effect movement ofthe plate |2| on rollers ||3. Mounted in conjunction with link |36 andcrank |32i are limit switches |45 and |41 to control the operation ofmotor |25.

A motor |59 supplied from a suitable source of energy is mounted inauxiliary housing 22. The output shaft |52 of the motor |59 is coupledto the input shaft of a gear reducer |5ll preferably of the worm geartype. The low-speed shaft |55 of reducer |55 has xed thereon a crankI5?. To the end of crank |52' is pivotally connected a link |58. A crank|58 has one end pivotally attached to link |58 and the other end rigidlyfixed to a shaft I 62 which projects into main housing Ill. This shaft|52 is mounted in bearings |84 and within main housing i8 has mountedthereon a pair of levers |556 and I8?. The other ends of levers I 56 andIS'I are pivotally connected to one end of operating shafts |58 and |68respectively. The other ends of operating shafts |68 and |88 arepivotally joined to one side of plate |25. Therefore operation of motorI5@ will cause levers |56 and ll to oscillate and thereby effectmovement of plate iilil on rollers H2. Mounted in conjunction with crankitil are limit switches IIll and I'II to control the operation of motor|50.

The structure immediately surrounding opening 38 is shown in detail inFigures 5-7 inclusive. The elongated members H8 are plates which areaesinet fastened to the main housing I and plate 40, as by Welding, onopposite sides of opening 38 as indicated in Figure 2. To eachvof thesemembers IIB is joined an elongated block |80, as by welding, asindicated in Figure "1. At spaced intervals pivot ins |82 are locatedextending through member IIB and block |80. Each 'pin |32 is providedwith bearings |84 and |86 adjacent either end. The member H8 is recessedto receive the head |88 of each pin |82 to prevent axial movement of thepin into and through the membe H3 and block |39. Each pin |82 projectsbeyond block iilii and has iixedly mounted on the end thereof thediagonal element H5. To one end ci each diagonal element is connected aroller i i2 by means of a short shaft |90 and suit able bearings (notshown) to permit the roller i I2 to rotate freely. The other end oi eachdiagonal element ii is biased by a spring ||4 positioned between thisend of element i I6 and plate ilo. To assist the performance of springM, the plate fili recessed as indicated at |92, see Figure '7, to securethe relative position of spring |4. As noted pre usly, bas lili) areconnected to plate @lil bounding opening 38 and each bar Hill previawith a Stellite edge I|i2 mounted thereon. -Plate iil rides on rollersH2 and has guide strips itil joined to its under surface to maintain therelative position of the plate on the roll-ers iiil. Hence it can beseen that bars and i222 constitute a valve seat and that plate iil constutes a gate valve head. `The springs lill tend to pivot theirrespective diagonal elements i it about the airis of their respectivepins Hill and move the rollers ||2 upivarclly t'iereby maintaining agas-tight contact between the plate ll and bar lili) and edges |02. 'inorder to prevent injury or damage to this valve structure, the rollerassembly is laterally oset from opening 38.

Each roller i |22 is independently lubricated. A grease fitting it isconnected to the shaft |99 mounted in diagonal element HG. The shaftiii@ hollow and communicates with the s i'or the roller iii. A ilexibletube lili! 'ltil are in communication with a manifold igure 4i) whichsupplied through a tericr of main housing il) by means of fittings tot.

The members iii have joined to one end thereoi' blocirs ist providedwith threaded bores 2| il to permit the roller i E2 and plate 2liassembly to be connected to the main housing il? by means of bolts 2li.

While this assembly has been described as constituting the valveimmediately above the Weigh hopper it, it is to be understood that thisstructure is substantially similar in all respects to the rollers litiand plate |2I assembly immediately below the hopper i8, and surroundingopening it.

The opera-tion oi the apparatus is as follows: Coal is introduced ontoconveyor belt i2 through or inlet from a bunker either directly orindirectly' and is carried to the end of belt i2 Where it is dumpedthrough opening 38 into hopper i8 Where it is weighed. Subsequentthereto, it is dumped from the hopper |8 and passes through opening itiland outlet 75 to a downspout or the liifze and is eventually introducedinto a zone of different gas pressure such as exists in a pressurefurnace or a pressure burner such e tubing 213:1 communicating with theeX l as a cyclone-type burner. The operation is carried out incontinuous batch fashion and consequently, the conveyor ceases tooperate during the discharging cycle `from the Weigh hopper. Theapparatus is generally divided into zones as regards pressure. The spaceoccupied by the conveyor as well as all apparatus preceding in thesystem is maintained continually at atmospheric pressure. The apparatussucceeding outlet 'l5 is continually under pressure. rlhe space occupiedby the weigh hopper i8 is a depressurizing zone and is alternatelysubjected to the pressure existing in the system and to atmosphericpressure.

The rollers ||2 and plate lili? assembly constitutes a gate valve toprevent ilow of 'gas through the system. Similarly the rollers li andplate |2| assembly constitutes a gate valve. For purposes of clarityhereinafter, the rollers I|2 and plate |20 assembly will be referred toas the top gas valve and the rollers H3 and plate I2| assembly will bereferred to as the bottom gas valve. An important concept of the presentinvention is that both gas valves are never open at the same time duringnormal operation.

n order to protect the gas valves and maintain them pressure tight atall coal is never deposited or dumped directly cn either of plates |23or IBI. A bulk material valve is provided ahead of each of the gasvalves in the system to operate before valve in .e to the flow or coalbefore the gas valve is closed. also the gas valve is opened before thebulle material valve permits a resumption oi coal flow.

The conveyor belt i2 constitutes the top bulla material valve and itsoperation is correlated with the top gas valve. The closure til olhopper it constitutes the bottoni bull' material valve and lil wiseoperation is eo ated with the bottom. gas valve.

Accordingly, the several valves cooperate in a cyo "c manner so thatboth gas valves are never open at the same time. This is accomplished bymeans of limit switches |113, iii?, i'i'ii and ill, the solenoid housedin compartment "ill, a suitable electrical circuit to control theoperation of motors 75, 26 and lili, the solenoid in compartment 'i4 anda limit switch on the weigh hopper levers, and another limit switch incompartment '14. This last liinit switch is closed when gate Eil isclosed. Operation of the Weighing electrical control is the saine asthat described in my Patent No. 2,372,746 and as used in commercial coalscales of modern manufacture. he cycle of operation is follows:

Consider as a starting point 'that the top gas valve is open, the bottomvalvel closed, the hopper IB is empty, and the conveyor is stopped.Since hopper gate EB is closed, the limit sii/'itch in housing i4 isalso closed, hence the electrical control circuit energizes the motoriii and conveyor belt I2 begins its motion and dumps coal throughopening 38 into the hopper i8. When hopper i3 receives a predeterminedWeight of coal, the limit switch actuated by the weigh levers opens themotor i6 control circuit thus stopping motor le, thereby stopping themotion of the conveyor belt i2. The motor ili is energized to close thetop gas valve. Thereafter, motor |26 is energized and causes the bottomgas valve to open. The solenoid is de-energized, permitting the Weightof the coal in hopper i8 to swing closure iis open against counterweightT2. The coal then passes out oi hopper i8 and through opening |04 andoutlet l5. When all the coal has left the hopper i8, the counterweight12 Will swing closure t8 shut. Thereafter, the solenoid is energized tohold closure 63 shut and motor |26 is energized to close the bottom gasvalve. The motor E! opens the top gas valve. The cycle is then completedand the apparatus is in the condition as described in conjunction withthe starting point.

The gas under pressure which is admitted to the depressurizing zone whenthe bottom gas valve is opened is quickly dissipated when the top gasvalve is opened which incidentally occurs before the weighing operation.Hence, the weighing operation takes place at substantially atmosphericpressure thereby eliminating weighing errors which otherwise might beintroduced should the weigh hopper I8 and the scale lever mechanism besubjected to substantially different pressures.

An alternative manner for operation of the gas valves is shown in Figure8. Here, a link Se@ is connected between one end of the top gas valve302 and a crank 354 mounted on shaft 30E. Also mounted on shaft 30.5 isa gear Stili which has gear teeth 308 over approximately one-fourth ofits periphery. Also, the gear 3% is provided with a radial extendingslot 3m. The gear 3d@ meshes with a similar gear 3l2 mounted on a shaft3i3. A link 3M is connected between one end of the bottom gas valve 31Sand a crank SIS mounted on shaft 3l9. Also mounted on shaft sie is agear 32E similar to gear This gear also meshes with a gear 322 in likemanner to gears 306 and 3|2. Gear 322 is mounted on shaft 323. Gear 395idoes not mesh with gear dit nor does gear 3I2 mesh with gear @22 aspairs of gears 3DS-3H and 320-322 are laterally offset. A motor 324supplied from a suitable source of power drives a gear reducer 325i. Thelow speed shaft 328 of reducer 32B has mounted at the end a Worm ESI.Meshing with the worm 335i is a worm gear 332 carried by a bearingmounted shaft 334. Fastened on shaft 334 is a crank 33t with a pin 33Sprojecting transversely at the end thereof. Accordingly, operation ofthe motor 32d will cause crank to rotate in a clockwise direction. Asshown in Figure 8, the movement of crank 33S will result in pin tiltbeing received in radial slot Sit and moving gear in a counterclockwisedirection for about 98 thereby moving crank to the position indicated as34S and in opening the top gas valve 302. Movement of gear Std resultsin a clockwise movement of gear :H2 to the same angular degree. Hence,the radial slots will align and the pin will pass into the radial slotin gear 3ft and move this gear counterclockwise for about 90 returningit to its original position. lso the gear 30E will be moved clockwisethe same degrec thereby closing the top gas valve Sti. As the radialslots in gears SI2 and 3222 now align, the pin S38 will pass into theradial slot in gear 322 and rotate this gear counterclockwise for about99. This movement causes 'ear 3253 to rotate clockwise the same angulardegree and results in opening the bottom gas valve lili and moving crankslt to the position indicated as 352. The radial slots in gears and nowalign and this permits the pin to be received in the radial slot in gearand rotate this gear about 90 in a counterclockwise direction therebyclosing the bottom gas valve 31d and returning gear 322 to its originalposition. The crank 335 and pin 33S have now traveled through 360 andthe gears and valves are again in their original positions. it thereforeis apparent that the desired movements of both gas valves can emanatefrom the single motor 324. rlherefore, when subjected to the electricalcontrolling circuit, the operation of motor can be controlled in harmonywith the cycle of operation, as previously described, to effectuate thedesired result.

Since pin 33t enters the various slots travelling parallel to the sidesof the slots, there is no hammer blow between the various parts. As aresult, the mechanism can be run very fast Without undue wear of partsor noise.

While this invention has been described in conjunction with specific.-embodiments, nevertheless, various changes or modifications obvious toone skilled in the art are within the spirit, scope and contemplation ofthe present invention as claimed.

I claim:

l. A system for feeding material to a zone having a pressure differentfrom atmospheric that comprises a gastight compartment having an inletand an outlet, a weighing device in said compartment, said weighingdevice having a closure element to permit discharge of material, anormally opened rst valve positioned in. said inlet, a normally closedsecond valve positioned in said outlet spaced from the closure elementof said weighing device, means responsive to the reception in saidweighing device of a predetermined amount of material to successivelyclose said first valve and open said second valve, and means responsiveto the discharge of material from said weighing device to successivelyclose said second valve and open said rst valve.

2. A system for feeding aggregate material to a zone having a pressuredifferent from atmospheric that 'comprises a conveyor, an airtightcompartment, a weighing device in said compartment, a normally open -rstvalve establishing communication between said conveyor and saidcompartment, a normally closed second valve establishing communicationbetween said compartment and said zone, means responsive to thereception in said weighing device of a predetermined amount of materialto successively stop said feeding means, close said first valve and opensaid second valve, and means responsive to the discharge of materialfrom said weighing device to successively close said second valve, opensaid first valve and start said feeding means.

3. A bulk material scale apparatus that comprises a housing divided intoa feeding compartment with an inlet therefor and a gastight Weighingcompartment with an outlet therefor, a weighing device in said gastightweighing device having a closure element to permit discharge ofmaterial, top valve means positioned between said compartments to cutoff the flow oi gas therebetween, bottom valve means positioned belowthe closure element of said weighing device and in said outlet to cutoif the ow of gas therethrough and controlling means connected to saidvalve means and correlating their movements to maintain at least one ofsaid valve means closed at all times.

4. A system for feeding material to a zone having a pressure differentfrom atmospheric that comprises a housing defining therein an inlet andan outlet, material storing means at atmospheric pressure connected tosaid inlet, said outlet connected to said zone, said housing dividedinto an atmospheric zone and a depressurizing zone, feeding meanspositioned in said atmospheric zone to receive material Afrom saidstoring means, a hopper in said depressuriaing zone to receive materialfrom said feeding means, scale means cooperating with said hopper toweigh the material therein, closure means on said hopper topermit thematerial to be discharged through said outlet into said zone, a top`valve establishing communication between said atmospheric zone and saiddepressurizing zone, :a bottom 4valve establishing communication.through Said outlet, and controlling ,means to operate the ,apparatusin continuous-batch 4fashion .so that `.one of said valves is maintainedclosed at all times.

f5. A system as defined in claim 4 wherein said feeding means and said.closure means constitute material valves and are `correlated by ,said.controlling means to prevent the deposition of .material .on said topand bottom valves,

6. A coal scale apparatus for use with a "furnace or the like having apressure other than atmospheric vthat comprises va 'housing :dividedinto a feeding compartment with an "inlet `.therefor and a gastightWeighing compartment with an outlet therefor, said inlet `ibeingconnected to a coal storing means, `a feeding means in said feedingcompartment Ato receive coal lfrom said storing means and to dischargethe -coal into said weighing compartment through an opening `:betweensaid compartments, aweigh hopper in said weighing compartment 'toreceive coal from said feeding means, closure ymeans .on said weighhopper to permit the coal to be discharged vthrough said outlet to thefurnace, a 'top `valve inthe opening between said compartments, .abottom valve in the outlet, land controlling means 'to maintain one of`said `valves closedat all times.

7. A -coal sca'leapparatusas defined in .claim 6 wherein :said feedingmeans .and said closure constitute coal'valves `and are correlated bysaid conw l2 trolling means to prevent deposition of coal on saidtop andbottom valves.

.8. .A coal scale apparatus for use with a furnace or vthe like having apressure other than atmospheric that vcomprises a housing definingtherein an ,inlet and -an outlet, said inlet being connected to :a coalstoring means, said outlet .being connected to coal receiving meanscommunieating with the furnace, said housing Adivided into an.atmospheric pressure zone and a depressur izing .-zone, feeding meanspositioned in said atmospheric pressure ,zone to receive coal vfrom thecoal storing means and to `discharge the coalintc the depressurizingzone, .a hopperin said depresf surizing ,zone to receive coal from saidvfeeding means, scale means cooperating with said -hop per to weigh thecoal therein, closure means on said hopper to permit the .coal to bedischarged through said outlet, a top gas valve between said atmosphericpressure zone and depressurizing zone, a bottom gas valve in saidoutlet, and controlling means to maintain `one vof said gas valvemeansclosed at all times` 9. A coal scale apparatus as dened in claim `8Whereinsaid feeding means and said closure constitute =coal valves andare correlated by said controlling means to prevent deposition of coalon said gas valves.

ARTHUR J. STOCK.

veferences Cited in the ille of this patent UNITED STATES PATENTS NumberName Date 570,299 Richards Oct. 27, 1896 2,138,356 Ryan Nov. 29, 19.382,294,551 Guest Sept. l, 1942 `2,372,746 Stock Apr. 3 1945

